In a letter from NUJ president James Doherty to South African president Thabo Mbeki, the union raised concerns that Mills’ death could be linked to his work and was not suicide as claimed by the Zimbabwean authorities.

“The National Union of Journalists shares with his family, colleagues and friends their grave concern at the circumstances surrounding Richard’s death (…)You will be aware that the current Zimbabwean government has a notorious record in relation to human rights and freedom of expression. Against this background we are requesting that you raise this incident in your discussions with Zimbabwean authorities to ensure that it is investigated in an open and transparent manner,” the letter said.

Mills, whose funeral was held in Belfast yesterday, was working undercover for The Times at the time of his death.

UPDATE – the International Federation of Journalists (IFJ), who had also called for an investigation into Richard’s death, have withdrawn their demand after his family announced they had accepted the result of a post-mortem, which suggested he had taken his own life.